This invention relates to a novel image display comprising a light-absorbing matrix and to a novel method for making that matrix. The novel image display may be a CRT (cathode-ray tube) intended for the display of television images, data or other types of information processed by an electronic system.
The viewing screen of an image display, such as a CRT of the aperture-mask type, comprises spaced elemental picture areas of luminescent material that are individually excited to luminescence. One expedient, used to improve the contrast of the luminescent image that is produced on the screen, is a light-absorbing or black matrix adjacent to the elemental areas of the picture. Such matrix has the effect of substantially reducing the intensity of ambient light that is reflected from the spaces between the elemental areas of the image.
Image displays including a light-absorbing matrix, methods for preparing a matrix, and materials constituting a matrix are disclosed previously, for example, in U.S. Pat. Nos. 3,558,310 to E. E. Mayaud and 4,049,452 to E. E. Nekut. One general method for preparing a light-absorbing matrix employs an intermediate tacky pattern. Variations of this general method are disclosed, for example, in U.S. Pat. Nos. 4,263,385 to T. R. Pampalone, 4,263,386 to P. Datta et al., 4,273,842 to S. Nonogaki et al. and 4,324,850 to Y. Tomita et al. In that general method, a layer of phototackifiable material is exposed to actinic light substantially in the pattern of the desired matrix, so that the exposed areas of the layer become tacky. Then, powdered matrix material is applied to the layer and the excess material is removed, leaving particles of matrix material attached to the tacky areas of the layer. Areas of luminescent materials of each of three different emission colors may be deposited by a similar procedure before the matrix is prepared.
Obviously, the matrix material should be strongly light-absorbing, strongly attractive to the tacky areas of the layer, and weakly attractive or even repulsive to the other areas of the layer. Also, the matrix material should be resistant to baking in air at elevated temperatures and to other subsequent fabrication procedures, and should be held in place after the tacky material is removed by subsequent baking.
Of all the matrix materials suggested in the prior art, graphite and carbon have been the most used and the most successful. That use has been principally with processes disclosed in the above-cited patents to Mayaud and Nekut. It is desirable to provide a matrix material which is better adapted for deposition on a tacky pattern. Such a material can improve both the method of preparing the matrix and the product of that method.